“…I would say, frankly, that our No. 1 priority in terms of legislation is immigration,” Napolitano told POLITICO’s Mike Allen at a breakfast marking the 10th anniversary of the agency. “It is high time for immigration reform.”

Napolitano appeared with the only other two secretaries to have led the department: former Homeland Security Secretaries Michael Chertoff and Tom Ridge, in their only joint appearance marking the department’s anniversary.

Napolitano also addressed reports that DHS has released immigrant detainees from detention centers as a cost-saving mechanism due to budget uncertainties tied to last week’s sequestration and other looming budget fights. Napolitano said that “several hundred” detainees were released — not “thousands,” as news reports from last week had indicated. She stressed that those moved from detention centers were low-risk, and that the process would continue “for the foreseeable future.”

“With sequestration looming and the end of the [continuing resolution] in a couple weeks, it’s like the perfect storm,” Napolitano said. “We really have to manage so many different things because we don’t have a budget.”

Napolitano said DHS secretaries are “between a rock and a hard place” on such issues, saying that even as Congress calls on the department to maintain thousands of beds for such detainees, the funding isn’t there and there isn’t the opportunity to shift money around. Ridge slammed Congress, saying the body is sticking DHS with needlessly complicated immigration questions.

“We’ve had three secretaries that had to do triage because Congress cannot find a way to create an immigration policy…a broad-based immigration policy for the United States of America,” he said, adding, “But let’s be very, very clear. The job of the secretary of Homeland Security… with regard to securing the borders would be a heck of a lot easier if the U.S. Congress would forget about partisanship [to] come up with a broad-based comprehensive immigration plan. The story ends right there,” he said to applause.

The impacts of sequestration are also evident beyond releases from immigration detention centers, Napolitano said.

“Now that we are having to reduce or eliminate basically overtime both for TSA and for customs, now that we have instituted a hiring freeze…we will begin today sending out furlough notices,” Napolitano said. “We are already seeing the effects,” adding that lines are “150 to 200 percent as long as we would normally expect.”

The three reflected on the brief history of the agency, which Napolitano called the “largest reorganization of the federal government since [the Department of Defense].” Chertoff, the second Homeland Security secretary, said that one of the challenges, but also the assets, of DHS, was that “no one was in the trenches…everything had to be dealt, really, from scratch.”

The organization was then able to focus on the question of, “How can we promote people operating in a joint fashion?” Chertoff said. “Because that’s really what the value proposition of the department was.”

As for the mission of DHS?

“It’s all about risk management,” said Ridge, the first department secretary. “It has been since Day 1.”

All three said technology has been a major driver of change at DHS, and Napolitano expressed hope that as technology continues to improve, air travel passengers will face fewer burdens going forward.